Electron discharge device



Aug. 26, 1952 w. c. BRowN 2,508,573

ELEcTRoN DISCHARGE DEVICE Filed oct, 25, 1949 2 SHEETS-SHEET 1 l i a 26 Y l:

T T I7/ 2 35 a3 2 @y w Af/ f5 20 INVENTOR W/LL/AM C. BROWN Aug. 26, 1952 vw. c. BROWN 2,608,673

ELEcTRoN DISCHARGE DEVICE Filed oet. 25, 1949 2 SHEETS--SHEET 2 /NVENTR W/LL/AM C. BROWN TTORNE'V Patented Aug. 26, 1952 `2.608,673 ELECrrR-:ON .DISCHARGE .DEVICE V f "William llrown, Weston, lMass.. assignorfto f Raytheon .'Manufacturing Company, Newton,

, Ma1ss., acorporation ofDelaware 5 .ApplicationOctober-225, 1949, Serial No.12'3;519 a je claims. (eda15-39).

`applicationrelates to eleetronfdischarge devices vv.and .more :partimilarly .to Yrrragnetrons :of the 'tunable-type. Y

In tunable magnetrons-oftheicavity type which are tunedwby theinserti'on :of tuning elements into the 'cavitieaiit has ybeenrdiscovered that the ,tuning elements themselves zresonate, thereby .sappinglpowerfrom the cavities andflowering the felciency of the device. .Morespecicallypas the .magnetron vfrequency is varied, the resonant .frequencies of .thetuning structure `Vary so that they `will coincide` with sthe frequency fof the 1magnetron at `several `points over the frequency range of operationtof `the magnetron. cnt; .these .points of coincidence the `power sappedby the ,tunerffrom tlflecavities is-so great that-operation of .the magnetron as `a microwave power -gen- -erator 'is unsatisfactory, if, indeedfoperation is at all possible.

`Applicant .has discovered th'atby 'strapping the lower r ends :ofv .the tuner elements which extend into the cavities,v interference -between rthe 'resonarices of rthetuner .andthe operation frequency of themagnetron may :be eliminated.

Applicant also provides herein a :mechanism particularly adaptable vto operation 'of this tuning structure `whereby `the magnetic field across A.the magnetron is varied synchronously with variations in the `tuning of the device.

y Further .objectstand advantages of this invention will, become .ap-parent vas [the `description progresses,referencelbeinghad to the accom-- panying ldrawings wherein.: i

, 'Fig. 1 .illustrates a longtudinal cross-sectional view of a .magnetronutilizing -applican-ts invention taken alonglline rII of ,2;

, Fig. .2 illustrates a partially '.brokeneaway transverse .cross-sectional view of 'the `device shown in Fig; 11 .taken alongiline 2-2 of Figi; Fig. `3 illustrates .a perspective view of `the tuning structure used :in Figs. 41 and `2jshowing the. details of the ...tuner strapping; and

l 4 illustrates .a ,modification of the .tuning vstructure shown `.inlignl which-may be-"used in place of the tuninglstructuretshown in .-Fig. 3. D

`lieferr'ing nowitoligs. V1.andw2., there is shown 'a .i'magnetron .comprising lan `anode .structure I 0 consisting. of an anodercylinder vI.I which may be of any desired material, such aswcopper. Extending radially inwardly from the 4inner 'surface of anode cylinder II are a plurality `of planar anode. members I2 Whose planar surfaces are parallel to the axis of cylinder .I I. A-node .members `I2 `may be `connected alternately at their lower edges `adjacent theirinner ends Yby a'pair anode 'cylinder-` IIL.

. -`2 of "straps I3 .to .preyen the anode structure. a l

.The ends of .anode .cylinder II are closedLby upper 4and lower `end plates I4. and ISVrespectively." Lower .-end plate. `I5 `has therein alfhle `cor-icentricwith the .axis of cylinder I'l inqvhich `is O.positioned a .magnetic ,pole piece `II5.' 1fole piece ,I6 has therein .a hole `concentrici,withthe axisof cylinder II and through which extends.a| cathode ,assembly ,I `'L CathodeY assembly -.I`1.f,comr prisesa metallic cylinder L8 which extendsjup Wardly into .cylinder .I.I` past the innerrendsfof anode members I2, and which 'is 4coated lwith electron-emissive .material on its outer" surface `over the area .adjacent `.thefinner ends tof anode .members I2. y

Cathode cylinder`|8, which is hollow., contains therein a heater coil I9, ,the upper end. of Vwhich connected to cylinder I8, andthe .lowerfeh'd of which `isconnected Lto a lead-in member 20, Heater coil .I9 .and .lead-in member .29 are in.- sula'ted from cylinder I8 'by `being 4.coated by any desired insulating material, 'such Cas, ior iexample, Alundum. 'The lower end of cathodelcylindei I`8eis .attached to a supporting cylinder2l Ysurrounding 'lead-.in member `2.0. 'Lead'in member 2'Ilis insulatedly supported with respect 'to supporting cylinder 2.I 'by any 'desired means., lsuch as an 'insulating seal, not shown. 1 Similarly, supporting cylinder LZI maybe insulatedly supjported with respect to magnetic .pole piece by .an 'insulating seal, not shown. a

VUpper end plate I4. has therein .aholeconcengtric with the axis of cylindery II and through which .extends 'a'magnetic pole piece 22.] Inside magnetic pole piece"22, :and concentric therewith, is a movable `pole piece 23which slidably engages the 'inner surface of pole piece .22. TIhe lowerend of movable pole piece 23 has therein"a,.`recess 214 to accommodate the' upper endy `of cathode cyl- 'inder I8. A'vacuum seal is :maintained in anode cylinder II by meansof `diaphragm vstructure 25 'attached to movable pole piece`f23 and upper end jpl'a'te I4. A magnetic eldisproducedbetween the `adjacent ends .of polefpieces I6` and 23 by any desired means, such as Ya permanent magnet connecting polepiecesA .I6 and 23`through an externa-l.magneticpa'th 26.

.In .order Yto remove microwave Venergy `frornthe cavities there .is provided `anoutputcoupling .comprising a-'loop `27| V.extending into .one fof `the cavities formedbyapairof anodemernbers I2. One .end of iconv-2H is connected toa lead-in member 28 which extends through the `wallwo'f `Concentric with lead-fin spurious .oscillationsfl'in pole piece 23. Extending downwardly from ring.

3|, and integral therewith, are a plurality of tuning elements 32. prises aprism having a substantiallytrapezoidal members l2. e y l. Alternate tuning elements 321are connected at their lower ends by a pair of straps 33. As.

Each tuning element com'- i ture.

shown here, the straps 33 set into notches 34'in the tuning elements. This form of v'notchingis 'similar `to the form of notchingnsed for connecting Yalternate anode members `l21 by the straps |3. However, the straps may be posif- ',tioned below the tuning elements and connected to thetuning elements by small extensions on downwardly as the tuning elements 32 are inlserted into the cavitiesl formed by anode memb ers I 2, said notches being largefenoug'h to prevent contact between straps 33 and the vanode members |2.v .A o.. I'Oneexplanation of the operationeof straps 33 'is as follows. The tuning structurej3lbehajles .asa resonant cavityat a frequency where the electrical distancefrom the lower end of one tuning lelement up to ring 3| and back tothe lower end of the next adjacent tuning element is equal to a half wave length of said frequency'. This may be 4termed the 1r mode resonance ofthe tuner. Thus it may be seen that adjacent tuner elements form resonant cavities in amanner substantiallyA similar to the manner in which adjacent anode .members l2 form resonant cavities. These cavities may bethought of. as a tank circuit having lumped parameters comprising inductance and capacitance. Due to close coupling between adjacent cavities, they maybe considered as a pluralityof sections of a transmission line which are connected in series. An analysis of these circuit parameters, which' include the inductance and capacitance'` of the tuner elements and the capacitance between the vtuner elements and the anode members, discloses that, in the `absence of straps in the lower ends of the tuning elements, each pair of adjacent .tuner elements which-comprises 'a transmission line section behaves as a low-pass lter `Whose upper cutoiv frequency isA the 1r mode of the tuner. Thus it may be seen that even though the dimensions of the tuning be shortened to y raise the 1r mode of the tuner 30 well abovethe operating frequency of the magnetron, lower frequencies will exist in the tuner structure which represents modes of resonance whereat a wave travelling along the transmissionv line made up of the cavities of the tuner structure will shift in phase lby a multiple of two 1r radians during lone complete journey around the tuning structure, thereby returning't'o the starting point in phase to reinforce the initial wave.

However, when the` tuning structure is strapped, an analysis of the tuning structure discloses each cavity thereof, .together with the #4 segments of straps, becomes a high-pass filter whose lower cutof frequency is the 1r mode of the tuner. Therefore, frequencies below the 1r mode of the tuner will not travel along the transmission line made up by the tuner cavities, and hence no resonances below the 1r mode of the tuner willnoccur therein. Since. the#v mode frequency of 'the tuner is made considerably higher -'than the operating frequencyof the magnetron `and since the strapped tuner will not resonate at frequencies below the 1r mode of the tuner, in-

terference due to coincident resonance of the .I ,tuner with the operating frequency of the magcross-section which conforms tothe'cross-section vnetron'is completely eliminated.

of the inner ends of the cavities formed by anodet `Referring now `to Fig. 4, there is shown another modiilcation of a strapped tuning struc- This comprises a ring 36 similar to ring 3| for attachment to the lower end of pole piece 23. 'Extending downwardly from ring 36 are tuner elements 31 similar to tunerY elements, 32 of the tuner 30. The low'erends of the-tuner elements 31 are all Aconnected together by a single circular strap set in notches inthe lower,

`-outer corners ofthe tuner elements 3".J f

It maybe seen that thevlowest frequency at which the tuner elements v3'! will resonate will be governed by the lgreatest distance' between points Vwhere adjacent tuner elementsy 31 aire shorted Vand 'points' where adjacent elements 31farefopen, forexample, the distance between the straps 38 andthe lower inner corners of the elements 31. This distance equals an electrical quarter' wave length of the lowest possible reseonant frequency'of the tuner, lSince this vdisltanceis made considerably less than a quarter 1wavelength of the operating frequency of the lfrequency to produce optimum operating conditions for the magnetron, andv applicant, by varying'the magnetic eld, is able to utilize a constant anode voltage for the device over the range of frequencies. Since va magnetron uses extremely high voltages which involve-large insulators, the use of a constant voltage. power supply rather "than a variable one produces a cheaper and more reliable device. This completes the description ofthe particular species of the invention illustrated herein. However, many modifications thereof rvvill'bel apparent to persons skilled in the art'. For example, the straps 33 and 38 may be placed at other positions onV the tuning structure and other configurations of tuning elements ymay be used, Furthermore, the anode members I2' need'not necessarily be strapped, and may beoffa dif# ferent shape from that used herein. Therefore, applicant does lnot wish tov be limited to rthe specic detailsof the embodiment of" theinvention disclosed hereinl except as dened by the appended claims.` f What is claimed is:

l. An electron discharge device vcomprising'an anode structure defining a cavity resonator hav# ing a plurality of `cavities,'a cathode adjacent said anode structure, and a tuning structure having a plurality of tuning elements extending into said cavity resonator, elements of said tuning structure being connected by conductive strapping at the ends thereof extending into said cavity resonator, said strapping being rigidly attached to said tuning structure and movable therewith.

2. An electron discharge device comprising an anode structure dening a cavity resonator having `a plurality of cavities, a cathode adjacent said anode structure, and a tuning structure having a plurality of tuning elements extending into said cavity resonator, alternate elements only ofV said tuning structure being connected by conductive strapping.

3. An electron discharge device comprising an anode structure defining a cavity resonator having a plurality of cavities, a cathode adjacent said anode structure, and a tuning structure having a plurality of tuning elements, an element of said tuning structure extending into each cavity of said resonator, and elements of said tuning structure being connected by conductive strapping at the ends thereof which extend into said cavity resonator, said strapping being rigidly attached to said tuning structure and movable therewith.

4. An electron discharge device comprising an anode structure defining a cavity resonator having a plurality of cavities, a cathode adjacent said anode structure, and a tuning structure having a plurality of tuning elements, an element of said tuning structure extending into each cavity of said resonator, and alternate elements only of said tuning structure being connected by conductive strapping.

5. An electron discharge device comprising an anode structure defining a cavity resonator having a plurality of cavities, a cathode adjacent said anode structure, and a tuning structure having a plurality of tuning elements extending into said cavity resonator, said tuning elements being connected at one end to said tuning structure and at the other end to conductive means which connect together only alternate elements.

' 6. An electron discharge device comprising an anode structure dening a cavity resonator having a plurality of cavities, a cathode adjacent said anode structure, and a tuning structure having a plurality of tuning elements, an element of said tuning structure extending into each cavity of said resonator, said tuning elements being connected at one end to said tuning structure and at the other end to conductive means which connect together only alternate elements.

7. An electron discharge device comprising an anode structure defining a cavity resonator having a plurality of cavities, a cathode adjacent said anode structure, a tuning structure having a plurality of tuning elements extending into said cavity resonator, elements of said tuning structure being connected by conductive strapping, means adjacent said cavity resonator forrproducing a magnetic eld across the space between said anode and cathode, and means coupled to said tuning structure for varying the strength of said magnetic field in response to variations in the frequency of said device.

8. An electron discharge device comprising an anode structure defining a cavity resonator having a plurality of cavities, a cathode adjacent said anode structure, a tuning structure having a plurality of tuning elements extending into said cavity resonator, elements of said tuning structure being connected by conductive strapping, and means adjacent said cavity resonator for producing a magnetic field across the space between said anode and cathode comprising a movable magnetic pole piece attached to said tuning structure.

9. An electron discharge device comprising an anode structure dening a cavity resonator having a plurality of cavities, a cathode adjacent said anode structure, a tuning structure vhaving a plurality of tuning elements extending into said cavity resonator, alternate elements of said tuning structure being connected by conductive strapping, means adjacent said cavity resonator for producing a magnetic eld across the space between said anode and cathode, and means coupled to said tuning structure for varying the strength of said magnetic eld in response to variations in the frequency of said device.

WILLIAM C. BROWN.

REFERENCES CITED The following references are of record in the leof this patent: 

